Technical Field
The present disclosure generally relates to cellular network selection and more specifically to cellular network selection for a 3GPP device/user equipment (UE) to access an Enhanced Packet Core (EPC) via an access network that is not a 3GPP defined access network.
Description of the Related Arts
A Voice over Wi-Fi (VoWiFi) call requires connection to an Evolved Packet Data Gateway (ePDG), which in turn needs to be selected by the UE. In addition, Public Land Mobile Networks (PLMNs) may have Lawful Intercept (LI) obligations that they are compelled to respect by laws in the jurisdictions in which the PLMN operates. Therefore, when the UE roams into a country or region or legal jurisdiction that is not belonging to the UE's Home PLMN (HPLMN), there may be LI obligations that need to be met and require the UE to select and establish a connection to an ePDG residing in a Visited PLMN (VPLMN) within the visited country/legal jurisdiction. Problems arise in enforcing the obligations by the HPLMN, the VPLMN or both.
There is currently no means defined in existing standards whereby the VPLMN can inform the UE, or the UE verify with the VPLMN, whether the UE can be allowed to select a HPLMN ePDG instead of a VPLMN ePDG. There is also no behavior defined for what the UE is to do upon receipt of this information.
The lack of a means for verification presents several problems. For example, it is not known how the UE can be instructed to select an ePDG in the VPLMN by the VPLMN when the UE has attached (i.e. has a Registered PLMN (RPLMN) in memory) via 3GPP access to that PLMN. In addition, if the UE has not attached to a PLMN (i.e. the RPLMN has been deleted according to 3GPP TS 23.122, subclause 5), but has authenticated with a PLMN via wireless local area network (WLAN) there is no means for that PLMN to instruct the UE to select an ePDG in that VPLMN.
PLMNs are sometimes identified by a fully qualified domain name (FQDN) that is not constructed from a PLMN Identity (ID) as defined in 3GPP TS 23.002 (i.e. a Mobile Country Code (MCC) and a Mobile Network Code (MNC)). For example, a PLMN may purchase a service provider that was not a PLMN. As such, until such time as the PLMN can operationally upgrade the infrastructure, there will be a period of time when a PLMN is advertised using non-PLMN codes. Current mechanisms have been identified as being an acceptable way to enforce LI in some circumstances, however these mechanisms only allow PLMN IDs to be provisioned and, as such, if a PLMN has LI requirements but advertises itself via a FQDN, there is no way for the HPLMN to configure this PLMN in the current data set.
Also, a VPLMN may identify its ePDGs via FQDNs, and a UE may only select an ePDG in a VPLMN using PLMN ID/code or Tracking Area (TA)/Location Area (LA), yet the FQDN is associated with an ePDG. There is currently no means to provision the UE to select an ePDG using such an FQDN to allow the VPLMN to meet its LI obligations via existing mechanisms.
Finally, if a solution is deployed to resolve the above problems, there is a possibility a VPLMN might abuse the mechanism to mandate the UE to use an ePDG in the VPLMN when the VPLMN has no LI requirement in order to capture potential lost roaming revenue.